Direct Port Manipulation on Multiple Boards

Using Arduino Programming Questions
#1

I have a library where I am using direct port manipulation for digital pins 9 and 10. I want this library to work for both the Arduino Pro Mini (ATmega328P) and the Arduino Mega (ATmega2560). The problem I am running into is if I reference "PORTH" in the libarary it fails to compile for the ATmega328P since it doesn't have a port H.

I have been trying to define the port in the preprocessor and while the code compiles it isn't working correctly. I have attached my most recent code where I am trying to define a macro so that I can use "PIN9_LOW()" and "PIN9_HIGH()" to toggle the pin and the macros would be set appropriately based on what board it was compiled for.

#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
  #define PIN9_LOW() "PORTH &= ~_BV(6)"
  #define PIN9_HIGH() "PORTH |= _BV(6)"
  #define PIN10_LOW() "PORTB &= ~_BV(4)"
  #define PIN10_HIGH() "PORTB |= _BV(4)"
#elif defined(__AVR_ATmega328P__)
  #define PIN9_LOW() "PORTB &= ~_BV(1)"
  #define PIN9_HIGH() "PORTB &= ~_BV(1)"
  #define PIN10_LOW() "PORTB &= ~_BV(2)"
  #define PIN10_HIGH() "PORTB &= ~_BV(2)"
#endif

This may not be the best way to do it and I am open to other suggestions.

#2

There are functions and arrays for that. See the SoftwareSerial. https://github.com/arduino/Arduino/blob/master/hardware/arduino/avr/libraries/SoftwareSerial/SoftwareSerial.cpp

Or the SoftwareWire: https://github.com/Testato/SoftwareWire/blob/master/SoftwareWire.cpp

It is this section:

port = digitalPinToPort(_sdaPin);
  _sdaBitMask  = digitalPinToBitMask(_sdaPin);
  _sdaPortReg  = portOutputRegister(port);
  _sdaDirReg   = portModeRegister(port);
  _sdaPinReg   = portInputRegister(port);
#3

Your 328 definitions are identical for LOW and HIGH....

Regards, Ray L.

#4

Peter_n: There are functions and arrays for that. See the SoftwareSerial.

But then the port access isn't direct. There is some extra code generated and it is a little bit slower than direct manipulation.

#5

Yes, it's a little slower. Use the defines for max speed, but fix them as RayLivingston wrote.

#6